1. Field of the Invention
This invention relates to metal treatment and, in particular, corrosion inhibition.
2. Art Background
Copper is a very important material for use in a vast number of applications. Not only is copper used for its aesthetic appearance in ornamental objects, but additionally the electronics industry heavily relies upon copper for its electrical conductivity properties. Whether copper is used in ornaments or in the high technology products, oxidation or corrosion of this metal seriously degrades its usefulness for the desired application.
A variety of treatments have been developed to prevent oxidation and corrosion with their associated adverse effects. The difficulties in finding a suitable oxidation and corrosion inhibitor are particularly great in the electronics industry. The treatment must not only produce effective oxidation and corrosion inhibition, but also the treatment must not prevent subsequent fabrication procedures such as soldering of the treated copper surface. Additionally, since corrosion or oxidation severely degrades electrical properties, an effective oxidation or corrosion inhibitor must be operative over an extended period of time.
Many compounds have been employed for corrosion or oxidation inhibition. For example, benzotriazole (BTA) has been used extensively in the electronics industry to produce a corrosion and oxidation-free surface that is amenable to subsequent soldering. Although BTA has been found to be quite useful, it is always desirable, if possible, to find and utilize inhibitors that have even greater lifetimes provided they also have the necessary properties for related operations such as soldering. In this regard, a variety of compounds have been tested as inhibitors. (See J. B. Cotton, Proc. 2nd International Congress of Metallic Corrosion, page 590, New York (1963), and J. B. Cotton and I. R. Scholes, British Corrosion Journal, 2, page 1 (1967).) However, despite a substantial effort, BTA is still considered the best inhibitor.